1. Field of Invention
This invention relates to a brake hydraulic control actuator for vehicles.
2. Description of Related Arts
A conventional brake hydraulic control actuator for vehicles is installed in hydraulic channels/circuits between brake master cylinders 70 and wheel brakes 80. It comprises solenoid valves 16′ controlling a brake fluid that flows in and/or out from the wheel brakes 80, 2 piston-type low pressure reservoirs reserving the brake fluid flown from the wheel brake 80 through the solenoid valves 16′, two pumps 14′, 15′ returning the brake fluid within the low pressure reservoirs to the hydraulic channels/circuits, and a motor driving the pumps 14′, 15′, and an actuator body on which all of the above-described elements are mounted.
The low pressure reservoir comprises a piston which partitions a cylinder bore into a hydraulic chamber and a gas chamber, and a compression coil urging the piston from the gas chamber side to the hydraulic chamber side.
If the gas chamber is exposed to atmosphere, foreign material such as moisture and dust fall into the gas chamber, thereby giving an adverse effect on the brake system.
In order to prevent the foreign material from entering into the gas chamber, some conventional methods introduce a technology where an opening of the gas chamber is closed by a lid that has vents, thereby allowing the gas chamber to communicate with the atmosphere. This technology, however, does not completely prevent foreign material from entering into the gas chamber because water may enter through the vents provided on the lid.
Japanese Provisional Patent Publication No. 2002-362344 (JP202-362344), FIG. 6 shows a typical, conventional hydraulic circuit which is also applicable to the present invention. FIGS. 3 and 4 shows an improved technology that is designed to prevent material from entering into the gas chamber. It provides a reservoir sealing structure where the opening of the cylinder bore is completely sealed by a protection cap.
In order to install the brake hydraulic control actuator on a vehicle body, as shown in FIG. 5, plural rubber mount 61 having shock absorbing effects are pre-mounted on lower right and left surfaces of the actuator body 60 and are installed in stays 63 of the vehicle side.
The above-described conventional brake hydraulic control actuator has the following points to be improved.
<A> The conventional technology of the foreign material preventive measure in JP2002-362344 is very effective in preventing the foreign material from entering because of the sealing structure of the reservoir. However, because of the air spring operation of the spring chamber due to the piston slide, the operational pressure of the reservoir increases more than necessary, thereby damaging the pressure reduction function during the control of the anti-lock brake system. Lower operational pressure of the reservoir is preferable so far as controlling of the anti-lock brake system.
<B> The protection cap sealing the opening of the cylinder bore elastically deforms the body outside of the cylinder bore and is fixed by crimping of the same. In order to complete crimping, the bottom portion of the actuator body needs to be designed sufficiently wider and thicker for crimping, which is not economical.
<C> Generally, to avoid the leakage of the brake fluid from the sliding/stroking portion of the pump to inside of the motor, fluid outlet holes for the brake fluid leakage are vertically formed in the actuator body, so that the leakage is discharged from an intermediate position between two accumulators installed at the lower portions of the actuator body. The brake fluid leakage cannot be disposed as it is. Therefore, the brake fluid leakage is reserved in a tube-like drain pan provided at the lower portion of the fluid outlet holes. However, a gap between two accumulators is often too narrow to secure sufficient space (volume) for reserving the brake fluid leakage in the drain pan.
<D> As shown in FIG. 5, the rubber mount 61 comprises many parts such as an installation bolt 63 directly fixed into the actuator body 60, a cylindrical outer sleeve 64 integrated with the installation bolt 63, a doughnut vibration isolation rubber 65 housed in the outer sleeve 64, a connection bolt 66 positioned in a central region of the vibration isolation rubber 65.
<E> The actuator body 60 requires to be small. It also requires simple structural layout for many functional components and channel/circuit formed in the actuator 60. However, the conventional technology for mounting the components in the actuator body 60 requires the installation bolt 63 of the rubber mount 61 to be installed directly in the actuator body 60, thereby restricting free and desirable layouts for the functional components and channel/circuit mounted within the actuator body 60.